Not even 36 hours after the company he co-founded went public, Facebook CEO Mark Zuckerberg got married. Secret engagement, secret wedding. Then Mark shared it on his Facebook timeline early evening on Saturday, May 19, 2012.

Just 36 hours after the company he co-founded went public, Facebook CEO Mark Zuckerberg got hitched in a secret ceremony held at his home on Saturday. He shared the shot from his Facebook page, above.

It was a clandestine engagement — the two have been together about nine years, friends tell aNewDomain.net — and it was a clandestine wedding, aNewDomain.net learned.

The some 100 guests coming to Saturday’s afternoon garden party at Zuckerberg’s Silicon Valley home thought they were there to celebrate Priscilla’s May 14 graduation from the University of California at San Francisco (UCSF) Medical School. But no.

Rather, a guest who asked not to be identified for this story told us, they very quickly discovered it was a wedding. The bridal gown was the giveaway.

“We were just floored,” he told aNewDomain.net. Chan received a simple ruby wedding ring, he added. She wore a wedding dress — Zuckerberg wore a business suit. Notice he did not fasten the top button on his suit. His sisters did! And sushi was served.

Editors on Wikipedia wasted no time updating the info on Zuckerberg’s entry. An update to Zuckerberg’s marital status a few minutes after aNewDomain.net shared the news. The Wiki entry said “the ceremony took place in Zuckerberg’s backyard under the guise that they were celebrating Chan’s graduation from medical school at the University of California, San Francisco, and receipt of her doctorate.”

Zuckerberg, who turned 28 May 14, the same day Chan, 27, received her MD from UCSF, has been a Time Magazine Man of the Year and two years ago became the world’s youngest ever billionaire.